Method for producing halftone multicolor images

ABSTRACT

A colored image or pattern formed of one or more colored hydrophilic colloid layers is produced on a permanent support by transferring onto such support in the presence of an aqueous liquid from a temporary support carrying the same, an unhardened colored hydrophilic colloid layer containing a photosensitive iron (III) complex which yields iron (II) ions on exposure to active electromagnetic radiation, exposing the thus-transferred colloid layer while in a substantially dry state to imagewise modulated active electromagnetic radiation, treating the exposed layer with an aqueous liquid comprising hydrogen peroxide or containing dichromate ions so as to effect hardening of the exposed regions of the colloid layer, and removing the nonexposed regions of such layer from the permanent support by washing with an aqueous liquid, these steps being repeated in sequence for each colored colloid layer transferred to the permanent support to constitute the ultimate colored image or pattern.

United States Patent Verelst et al.

[54] METHOD FOR PRODUCING HALFTONE MULTICOLOR IMAGES [72] Inventors: Johan Lodewljk Verelst; Albert August Reyniers, both of Kontich, Belgium [73] Assignee: Gevaert-Agta N.V., Mortsel, Belgium [22] Filed: May 15, 1969 [211 App]. No.: 825,056

[30] Foreign Application Priority Data May 15, 1968 Great Britain ..23,077/68 [52] US. Cl.v...- ..96/30, 96/92 [51] Int. Cl ..G03c 1/64 [58] Field of Search ..96/83, 92, 75, 28, 30

[56] References Cited UNITED STATES PATENTS 778,947 1/1905 Brasseur ..96/83 1,954,325 4/1934 Martinez ..96/92 X FOREIGN PATENTS OR APPLICATIONS 886,716 10/1942 France ..96/75 5] Feb. 15,1972

Primary Examiner-Norman G. Torchin Assistant Examiner-Alfonso T. Suro Pico Attorney-William J. Daniel [5 7] ABSTRACT A colored image or pattern formed of one or more colored hydrophilic colloid layers is produced on a permanent support by transferring onto such support in the presence of an aqueous liquid from a temporary support carrying the same, an unhardened colored hydrophilic colloid layer containing a photosensitive iron (Ill) complex which yields iron ([1) ions on exposure to active electromagnetic radiation, exposing the thus-transferred colloid layer while in a substantially dry state to imagewise modulated active electromagnetic radiation, treating the exposed layer with an aqueous liquid comprising hydrogen peroxide or containing dichromate ions so as to effect hardening of the exposed regions of the colloid layer, and removing the nonexposed regions of such layer from the permanent support by washing with an aqueous liquid, these steps being repeated in sequence for each colored colloid layer transferred to the permanent support to constitute the ultimate colored image or pattern.

27 Claims, No Drawings METHOD FOR PRODUCING HALFIONE MULTICOLOR IMAGES The present invention relates to a recording and reproduction process for producing colored colloid patterns corresponding with informationwise modulated electromagnetic radiation. The present invention more particularly relates to a process for producing halftone and linework multicolor images and to materials used therefor.

The production of halftone color images is of interest in the field of design, e.g., in the production of color decorative patterns, color wiring and circuit diagrams, cartography, color proofing and in the production of transparencies for diaor overhead projection.

Especially in the color field of the graphic art there is a great need for a simple and fast technique ofi'ering color proofs" of high quality and reproducibility.

Color proofing materials serve to produce a showing proof for submission to the printer and its client to give an idea of a multicolor halftone reproduction as will be produced by the successive printing in register with the separate standard inks: yellow, magenta, cyan, and black.

The color proof makes it possible to determine whether corrections have to be made to the separation halftone negatives, with the aid of which the printing plates have to be produced.

Known color proofing systems may be catalogued according to the way, wherein the multicolor proof is built up and can be inspected.

According to a first system, which offers a less good imitation of the final printing results, separate monocolor halftone transparencies are produced, which must be laid in register and inspected diascopically or against an opaque background.

According to a second system the multicolor print is built up on one permanent support having the desired opacity. Within that system several embodiments exist. According to one technique multicolor halftone images are produced e.g., by means of silver halide light-sensitive materials incorporating color couplers or dyes that can be bleached or transferred imagewise. The processing conditions applied are rather critical and, when color couplers or dyes take part in a chemical processing it is not easy at all to find or to produce compounds, which have an absorption spectrum practically identical to that of the standard printing inks and which at the same time fulfil specific reactivity requirements.

According to another technique photochemically hardenable pigment layers are successively applied by wiping on or whirler coating or roller coating on a same permanent support, and each layer successive to its coating is exposed through a proper separation negative and developed by removing the nonexposed portions.

Owing to the coating procedure this technique yields irreproducible results and is cumbrous.

According to a further technique a same support is colored by means of properly selected dye solutions imagewise penetrating through successively coated imagewise exposed and photohardened colloid coatings, which are removed integrally after the formation of the separation color image in the support.

According to a further technique the color proof print is formed on an electrophotographic paper by successive exposures and developments. The electrophoretic development applied here is very critical and the apparatus employed expensive and to be handled by skilled people.

According to a further technique a color proofing system is offered wherein a multilayer material having a temporary support and an organophilic light-sensitive pigmented coating is transferred to a single base material by the steps of:

i. removing a protective sheet, which uncovers a pressuresensitive adhesive layer on the pigment coating,

2. rolling down the pigment coating with the adhesive layer onto a base with a hand roller, and

3. removing the temporary support by peeling off, thus leaving the pigment coating attached to the permanent support.

The transferred pigment coating is then exposed to a proper halftone separation negative in a vacuum frame. After exposure the proofing is developed with an organic liquid and the unhardened parts removed by light swabbing. After drying the process is repeated for producing in superposition a reproduction of the yellow, magenta, cyan, and black printer prints.

The composition of this transfer material is rather complicated because of the need of a special adhesive layer. The said transfer material is less attractive for its development with organic solvents. Further transfer can be difficultly carried out without blisters.

According to known photographic processes hardened colloid patterns corresponding with electromagnetic radiation patterns are produced and developed to relief patterns by means of an aqueous liquid using a nonlight-sensitive hydrophilic colloid or polymer, which is insolubilized or crosslinked by means of a compound that is produced by irradiation of a photosensitive compound. In one of said processes dichromated hydrophilic colloid layers e.g., layers containing dichromated gelatin or gum arabic (ref. P. Glafkides, Photographic Chemistry, Fountain Press, London, Vol. ll 1960), p. 669-674) are used.

Colloid layers sensitized with dichromate suffer, however, from variations in sensitivity with age and have an inherent undesirable color. After drying, the sensitivity first rises, then falls over a period of hours. This can be tolerated in monochrome work but will give rise to less accurate color rendering in tricolor work.

Another know n process operates with an hydrophilic crosslinkable colloid such as gelatin containing a light-sensitive polyazide compound e.g., a water-soluble aromatic polyazide compound such as 4,4-diazido-stilbene-2,2'-disulphonic acid. The azide system invites interest because of the favorable stability of the coating solutions and coated layers.

Suitable water-soluble diazido aryl compounds are described in the French Pat. specification 886,716 filed Oct. 10, 1942 by Kalle AG. Exposure to light causes the azide group to break down nitrogen is set free and free radicals are generated. These radicals rapidly couple with the molecules of the hydrophilic c olloid forming cross-links and reduce thereby the solubility of die colloid in water.

According to another process a light-sensitive compound is used which on exposure produces a substance, by means of which in a reaction following the exposure an active hardening species is formed.

In such a type of process a hardenable hydrophilic colloid is used, which is mixed with a photosensitive iron(lll) complex compound that on exposure to active electromagnetic radiation produces iron(ll) ions, by means of which on oxidation an active species for the reduction in water-solubility of the surrounding hydrophilic colloid is formed.

It is an object of the present invention to provide a recording and reproduction process suited for the production of colored colloid patterns corresponding with informationwise modulated electromagnetic radiation.

It is more particularly an object of the present invention to provide a recording and reproduction process, which is especially suited for producing high quality halftone and linework multicolor prints in an economic, highly reproducible and easy way.

It is also an object of the present invention to provide the proper materials for carrying out such a process. Other objectives and advantages of the invention will become apparent from the description.

The process of the present invention has certain aspects, which lie at the root of the particular advantages set forth in the above objects.

According to one of said aspects of the process of the present invention the colored colloid relief patterns are formed by means of an aqueous processing.

According to another aspect of the present invention multilayer colored colloid relief patterns are formed on a single permanent support starting from colored electromagnetic radiation-sensitive hydrophilic colloid layers, which are transferred in wet state in superposition to said single permanent support by stripping off before exposure from a preferably relatively hydrophobic temporary support.

According to an aspect of a preferred embodiment of the present invention colored electromagnetic radiation-sensitive hydrophilic colloid layers are formed on a temporary support from a coating composition which contains diffusion-resistant coloring substances and particularly stable (in comparison with dichromated gelatin) radiation-sensitive substances in a desired amount already in the coating stage. In other words no coloring or light-sensitive ingredients are introduced by imbibition which is difficult to control and yields less reproducible results. Moreover, the exposure of the colloid layers can proceed in substantially dry state, which excludes chemical attack of the exposure apparatus and offers a real advantage to the operating personnel.

According to a characterizing aspect of the most preferred embodiment of the present invention superposed multilayer colored colloid patterns are produced wherein each of the transferred colloid layers after its imagewise exposure to active electromagnetic radiation is hardened in the exposed areas by means of an aqueous hardening treatment, as a result of which the hardened colloid portions become anchored to underlying colloid portions or parts of an underlying colloidcontaining layer e.g., a hydrophilic subbing layer by the same hardening reaction that effected the imagewise hardening of the exposed colored colloid layer involved.

Any possible frilling off of the colored colloid coating during washoff development, which is so common a difficulty in processes involving a washoff treatment of transferred colloid coatings, is overcome in this way.

According to another aspect of the process of the present invention which relates to the production of high-quality multicolor images, differently colored electromagnetic radiationsensitive hydrophilic colloid layers are transferred in wet state from a temporary support to a single permanent support, which-when used in color proofing-4s preferably an opaque hydrophilic or hydrophilized support resembling as much as possible the printing stock. Each transferred colloid layer is exposed separately in register on the single permanent support through a properly selected separation negative while directing the exposed colloid layer to the radiation source during the exposure.

The process of the present invention for the production of (a) colored colloid pattern(s), wherein (a) hydrophilic colored colloid layer(s) is (are) used, which is (are) hardened in the irradiated portions by means of an active species formed during or after the informationwise exposure to active electromagnetic radiation of a photosensitive substance, contains the steps of:

l. transferring a colored hydrophilic colloid layer containing a said photosensitive compound and a hydrophilic colloid that undergoes a reduction in water-solubility by said active species from a temporary support, which is relatively hydrophobic in respect of a permanent support, to which said layer has to be transferred, to said permanent support by pressing it in the presence of an aqueous liquid (in other words in moist or dampened state) against said colloid layer, and removing the temporary support, thus leaving the said layer on the permanent support, exposing the transferred colloid layer in substantially dry state to active electromagnetic radiation, which is modulated according to the information to be recorded,

. developing the exposed layer by means of an aqueous liquid forming by washoff a colored relief pattern, and when superposed colored colloid patterns on a single permanent support have to be produced-repeating the steps (1), (2), and (3) with said hydrophilic colloid layers having a color as desired.

According to a particular embodiment of the present invention (a) hydrophilic colored colloid layers(s) is (are) used that contain(s) a water-soluble photosensitive aromatic polyazide compound, by means of which on exposure to active electromagnetic radiation an active species is formed that reduces the solubility in water of the hydrophilic colloid at the exposed portions.

According to a preferred embodiment of the present invention (a) hydrophilic colored colloid layer(s) is (are) used that contain(s) (a) photosensitive iron(lll) complex compound(s), which produce(s) iron(ll) ions on exposure to active electromagnetic radiation, which iron(ll) ions are oxidized by an oxidizing agent yielding an active species for the reduction in solubility in water of the hydrophilic colloid at the exposed portions.

Thus, according to a preferred embodiment of the present invention colored colloid patterns are produced by a process wherein:

l. a colored hydrophilic colloid layer containing (A) a lightsensitive iron(lll) complex compound, by means of which on exposure to active electromagnetic radiation iron(ll) ions are produced, and (B) a hydrophilic colloid that undergoes a reduction in water-solubility on oxidizing said iron(ll) ions with a suitable oxidizing agent, is transferred from a temporary support to a permanent support by pressing it in the presence of an aqueous liquid against the said layer and removing the temporary support, thus leaving the said layer on the permanent support,

2. after drying the transferred colloid layer is exposed to active electromagnetic radiation, which is modulated according to the information to be recorded, thereby informationwise producing iron(ll) ions,

. the exposed colloid layer is treated with an oxidizing liquid, by means of which the iron(ll) ions are oxidized and the reaction agent(s) is (are) formed that produce(s) a reduction in water-solubility of the colloid layer at the irradiated areas,

4. the unhardened or insufficiently hardened portions of the colloid layer are removed by means of an aqueous liquid washing off the said portions, and when superposed color patterns on a same permanent support have to be produced, the steps (1), (2), (3), and (4) are repeated with said hydrophilic colloid layers having a color as desired.

Preferably the informationwise exposure is a contact exposure carried out through a transparency, which can be a halftone or a linework transparency. The exposure for producing multicolor reproductions is an exposure in register, which is preferably carried out with appropriately selected separation negatives held in contact with the radiation-sensitive colloid layer.

According to said process multicolored halftone prints, the halftone dots of which have a size largely independent of the exposure time, can be produced. This property, the reproducibility of the results and the fact that halftone dots of high quality (of particularly good sharpness) are produced makes that process especially suitable for high-quality halftone multicolor work.

The high reproducibility of the results obtained by the application of the said process is particularly due to the fact that the photosensitive ingredient(s) and dyestuffs of the photosensitive colloid layer are already before the coating of the said colloid layer contained in its coating composition in a properly determined amount. Indeed, less reproducible results are obtained when incorporating one of the ingredients of the colloid layer after coating e. g., by imbihition.

The washoff treatment applied in the present invention is very simple and provides copies having an excellent sharpness.

The keepability of the unexposed colloid layers is very good.

According to a preferred embodiment the light-sensitive iron(lll) complex compounds, which on exposure to active electromagnetic radiation yield iron(ll) ions, are of the type wherein the iron(lll) ion is complexed by means of ligands having an electron-donating character in respect of the iron(III) ion. Such iron(III) complexes are preferably derived from a polybasic acid that forms complexes of the formula (Fe A wherein represents: y the valency of iron (in the present case 3), z the valency of the organic acid and x that of the resulting complex ion. According to P. Glflfl(ldCS in Photographic Chemistry, Vol. I, Fountain Press London (1958), p. 422, the relation Fur-y must apply, n being the number of molecules of acid.

lron(IlI) complexes that are used more preferably according to the present invention are complex oxalates, complex tartrates, and complex citrates of iron(III) ions.

The sensitivity of the colloid layer increases with rising concentrations of photosensitive compound. The incorporable amount of the light-sensitive iron(III) complex compound and water-soluble aromatic polyazide compound is limited by the concentration, at which crystallization of the said compounds in the colloid layer starts. Consequently, preferably the best water-soluble complexes are used or mixtures of these complexes that do not so easily crystallize. Preferred in this respect is ammonium iron(III) oxalate. The recording layer may contain up to 40 percent by weight of ammonium iron(III) oxalate without crystallization in the colloid. Preferably the hardenable colored colloid layer contains to percent by weight of the iron(III) complex calculated on the weight of the dry hydrophilic colloid(s) e.g., gelatin.

In principle it is not necessary to use light-sensitive iron(III) complexes, since a number of transition metals of variable valency form complex polybasic acid salts in the same way as iron (see the above-cited P. Glafkides reference p. 423). The metal ions in the said complexes have to lose a valency by the action of light. Metals, which in this respect resemble iron are e.g., cobalt, chromium, and manganese. The most light-sensitive complex salts are the oxalates followed by the tartrates. The citrates are the most stable of them. The light-sensitivity of the iron(III) complex salts is in the wavelength range of 360-450 Nm. By the action of light the iron(III) ion in the complex compound loses a valency and becomes an iron(II) ion no longer masked in a complex salt structure.

After the exposure the iron(ll) ions are oxidized with a suitable oxidizing agent from which upon reduction the necessary hardening agent(s) is (are) formed for insolubilizing the hydrophilic colloid of the colored recording layer.

Preferably used hardenable colloids are hydrophilic watersoluble colloid polymers containing active hydrogen atoms as are present e.g., in hydroxyl groups and carbonamide groups. Both qualitative characterization and quantitative determination of active hydrogen can be carried out by the procedure known as the Zerewitinoff active hydrogen determination. Hardenable colloids containing active hydrogen atoms are e.g., polyvinyl alcohol, polyacrylamide or gelatin, and other film or stratum-forming proteinaceous colloids.

In the present invention best results are obtained with hydrophilic water-soluble colloids that possess the property of sol-gel transformation" such as gelatin, which offers an easy transfer and good adherence to the permanent support. Solgel transformation is explained by R. J. Croome and F. G. Clegg in Photographic Gelatin, The Focal Press, London (1965) pages 37-39.

The above hydrophilic colloids may be used in admixture with proper latent hardening agents, cross-linking agents,

and/or monomers that can be polymerized catalytically. C'ompounds, which are suitable in this respect, are described in the U.S. Pat. No. 3,101,270 of Helene D. Evans and Fritz W. H. Mueller issued Aug. 20, 1963 and U.S.-Pat. No. 3,136,638 of Andre K. Schwerin, Walter F. Burrows and Helene D. Evans, issued June 9, 1964 wherein the polymerization of unsaturated organic compounds by means of radiation-sensitive iron compounds as photoinitiators and the production of a photosensitive stencil and a process for making same are disclosed.

Any monomer containing the grouping CHFC/ compatible with the selected hydrophilic colloid, preferably gelatin, may be used. A catalytically polymerized monomeric compound suitable for use in combination with gelatin is acrylamide, which compound is soluble in water and compatible i.e., homogeneously miscible with gelatin.

In admixture with the hardenable hydrophilic colloid(s) optionally mixed with such catalytically polymerized compound, a cross-linking agent can be used to increase the efficiency of the hardening. For that purpose an unsaturated compound containing at least two terminal vinyl groups each linked to a carbon atom in an unbranched chain or in a ring can be used. A preferred cross-linking agent is N,N'-methylene-bis-acrylamide.

Any of the known organic or inorganic peroxides of hydroperoxides may be used to induce the polymerization of the vinyl monomers such as e.g.', hydrogen peroxide, ammonium persulphate, methyl hydroperoxide, ethyl hydroperoxide, cumene hydroperoxide, etc.

A large number of monomers, cross-linking agents, iron(III) salts and per-compounds which can be used in the production of a colloid pattern by catalytical polymerization upon informationwise irradiation with electromagnetic radiation in the sensitivity spectrum of a photosensitive iron(III) complex compound are described in the U.S. Pat. No. 3,101,270 of Helene D. Evans and Fritz W. H. Mueller, issued Aug. 20, 1963.

In the production of superposed multicolor colloid patterns the dyes used in the photosensitive colloid layers have to be resistant to diffusion and chemically inert in the processing and washing liquid(s) as much as possible. When using in color proofing they have to match with the absorption spectrum of the standard inks as close as possible. Particulars about standard color inks can be found in H. M. Cartwright, llford Graphic Arts Manual 1962) Vol. I, pp. 502504.

There exist cold" and warm color standards. Cold color tones are e.g., standardized in the U.S.A. in the GATF-Color Charts and in the German Standards DIN 16508 and 16509. Warm color tones are e.g., standardized in the German Standard DIN 16538.

The cold color standards are characterized by the use of fairly pure magenta pigments, mostly insolubilized Rhodamine and Phloxine-dyes, which have a very low side-absorption in the blue region of the spectrum.

The warm color standards are characterized by the use of insolubilized azo dyestuffs. Said dyestuffs are more resistant to solvents e.g., alcohol than the Rhodamines and Phloxines, but they possess a much higher side-absorption in the blue region of the spectrum.

It has been found experimentally that pigments, which are very poorly soluble or insoluble in water and organic liquids of the alcohol or polyhydric alcohol type e.g., glycerol are fulfilling the requirements of resistance to diffusion. Pigment dyes that are applied from an aqueous dispersion are used preferably, though the use of substantive dyes that are chemically linked to a colloid or polymer is not excluded. For color proofing purposes the hardenable colloid layer contains pigments in a concentration so high that the optical density in the wavelength range of maximum absorption is at least 0.35.

Apart from the use of dyes, the absorption spectrum of which has to satisfy particular requirements for color proofing, all colors are considered e.g., cyan, light-cyan, magenta, warm magenta, black, yellow, green, brown, orange, red, white blue as well as metallic colors such as pale gold, rich gold, copper, and silver. In other words when using the term color in the present invention it is meant to encompass all pure and mixed colors as well as black and white.

Nonmigratory pigments suitable for use in the present invention are known by the name PIGMOSOL and COLANYL dyes. PIGMOSOL" and COLANYL" are trade marks of Badische Anilin- & Soda-Fabrik A.G., Ludwigshafen/Rh., W.-Germany, for organic pigment dyes, which are mixed with a dispersing agent for aqueous medium. These pigment dyes excel in resistance to light, heat, acids, bases, ox-

idizing agents, and solvents. They are insoluble in hydrophilic colloids such as gelatin.

The black pigment for the black-toned part image is preferably carbon black.

Even if the pigments are completely inert in the aqueous processing and washing liquids they may to some extent stain the permanent support at the nonexposed areas as a result of simple adhesion forces. In order to avoid a direct contact of the pigment(s) with the permanent support the pigment coating on the temporary support is overcoated with a hydrophilic colloid layer (top layer), which does not contain pigments or dyes for forming the image. On transfer of such composite coating the top layer comes into contact with the permanent support and is sandwiched between said support and the pigmented coating. The top layer contains the same colloid(s) as the colored layer and is preferably of the same composition as the pigmented coating except for the presence of the visible image-forming pigment(s) or dyes thereon. The top layer, however may contain a small amount of translucent pigments e.g., silica particles protruding from the layer and being a few microns thicker than the top layer. They avoid sticking of rolled up sheet material at relatively high (e.g., 60 percent) relative humidity. The top layer contains e.g., 1 to 1.5 g. of gelatin per sq. m.

In order to obtain images with a good resolution, relatively thin radiation-sensitive colored colloid coatings are preferred. Preferably they have a thickness in the range of 1p. and p. Good results are obtained with colored colloid layers containing 2 to 10 g. of gelatin per sq. m. Very good results are obtained with colored layers having a thickness of 4 to 5p. and containing 2.5 to 3 g. of gelatin per sq. m. The colloid layers preferably contain at least 50 percent by weight ofgelatin.

The adhering power of the transferable coating to its temporary support, preferably a flexible one, has to be adjusted in such a way that an easy stripping off from the temporary support is possible after pressing the pigment coating into contact with the permanent support. Therefor, a relatively hydrophobic temporary support e.g., an unsubbed cellulose triacetate sheet, a polystyrene sheet, or sheet of copoly(vinyl acetate/vinyl chloride) and a permanent support having a hydrophilic surface e.g., a polyethylene terephthalate support subbed for adhering gelatin coatings can be used, e.g., a hydrophobic support subbed as described in the Belgian Pat. specification 72 l ,469 filed Sept. 27, 1968 by Gevaert-Agfa N.V. According to a preferred embodiment the photosensitive coating is composed in such a way that its adherence to the temporary support in wet state is less than in dry state. This can be attained by the addition of hygroscopic agents e.g., a water-soluble organic hygroscopic compound e.g., glycerol and the use of wetting agents and plasticizing agents. After washoff treatment the colloid relief pattern is dehydrated (unswelled) with a water-attracting alkanol/water mixture preferably an ethanol/water mixture in order to provide a sufficient mechanical strength and to prevent damage when transferring a further colloid layer thereon. A temporary support having a repelling power for wet gelatin coatings is e.g., the modified paper base used in the Bromolith" material (Bromolith is a registered trademark of Gevaert-Agfa N.V. for a light-sensitive paper offset plate). The said paper base is coated with a layer of insolubilized polyvinyl alcohol or a layer of alginic acid insolubilized with an alkali earth metal salt.

The permanent support may be rigid as well as flexible and only must present by itself or by means of (a) subbing layer(s) a good adherence in wet as well as in dry state for the transferable hydrophilic colloid coating.

Depending on the use of the multicolor print the permanent support is transparent or opaque. So, it is possible to use metal layers or sheets, glass, ceramics, resin supports and paper impermeabilized for the processing and washing liquids.

For purposes such as color proofing wherein several exposures have to be effected in register it is necessary to use a resin support with high dimensional stability.

Resin supports characterized by a high mechanical strength and very low water absorption and consequently high dimensional stability in dry and wet state can be formed from a linear polyester e.g., a linear polyester e.g., polyethylene terephthalate, Good results as to dimensional stability are obtained with aluminum sheets sandwiched between two high wet-strength paper sheets although this material is rather expensive.

Permanent resin supports can be made opaque by coating them with a matted subbing layer or by matting or coloring them in the mass. The matting may be effected by pigments known therefor in the art e.g., titanium dioxide, zinc oxide. and barium sulphate. Matting can also be obtained by producing a blush coat" as described e.g., in Canadian Pat. specification 654,438 of Labelon Tape Co., issued Dec. I8, 1962.

Hydrophobic resin supports to be used as permanent support according to the present invention are coated with one or more subbing layers for a hydrophilic colloid layer.

Preferred subbing layers for use on a permanent hydrophobic resin support e.g., a polyethylene terephthalate support are described in the Belgian Pat. specification 721,469 filed Sept. 27, 1968 by Gevaert-Agfa N.V. In the said specification, which has to be read in conjunction herewith a sheet material is claimed which successively comprises a hydrophobic film support, a layer (A), which directly adheres to the said hydrophobic film support and comprises a copolymer formed from 45 to 99.5 percent by weight of at least one of the chlorine-containing monomers vinylidene chloride and vinyl chloride, from 0.5 to 10 percent by weight of an ethylenically unsaturated hydrophilic monomer, and from 0 to 54.5 percent by weight of at least one other copolymerizable ethylenically unsaturated monomer; and a layer (B) comprising in a ratio of 1:5 to 1:0.5 by weight a mixture of gelatin and a copolymer of 30 to 70 percent by weight of butadiene with at least one copolymerizable ethylenically unsaturated monomer.

For ease of reference, the layer formed from the copolymer of vinylidene chloride and/or vinyl chloride is hereinafter referred to as the vinylidene chloride copolymer layer, and the layer formed with the mixture of gelatin and butadiene copolymer is hereinafter referred to as the butadiene copolymer layer.

The vinylidene chloride copolymer comprises from 0.5 to 10 percent by weight of ethylenically unsaturated hydrophilic monomeric units. These units may be derived from ethylenically unsaturated monoor dicarboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid. Other hydrophilic units, e.g., those derived from N-vinyl pyrrolidone, may be present.

The vinylidene chloride copolymer may be formed from vinylidene chloride and/or vinyl chloride and hydrophilic monomeric units alone in the ratio indicated above. Preferably up to 54.5 percent by weight of other recurring units, for instance acrylamides, methacrylamides, acrylic acid esters, methacrylic acid esters, maleic esters, and/or N-alkylmaleimides, may also be present.

Suitable vinylidene chloride copolymers are e.g., the copolymer of vinylidene chloride, N-tert.-butyl acryla mide, n-butyl acrylate, and N-vinyl pyrrolidone (70:23:324),

the copolymer of vinylidene chloride, N-tert.-butyl-acrylamide, n-butyl acrylate, and itaconic acid (70:2 l :5:4),

the copolymer of vinylidene chloride, N-tert.-butyl-acrylamide, and itaconic acid (88: 10:2),

the copolymer of vinylidene chloride, n-butylmaleimide,

and itaconic acid (90:8:2),

the copolymer of vinyl chloride, vinylidene chloride, and

methacrylic acid (65:30:5

the copolymer of vinylidene chloride, vinyl chloride, and

itaconic acid (7022614),

the copolymer of vinyl chloride, n-butyl acrylate, and

itaconic acid (66z30z4),

the copolymer of vinylidene chloride, n-butyl acrylate, and

itaconic acid 18:2),

the copolymer of vinylidene chloride, methyl acrylate, and

itaconic acid (90:8:2),

the copolymer of vinyl chloride, vinylidene chloride, N-

tert.-butylacrylamide, and itaconic acid (50:30: l 8:2).

All the ratios given between brackets in the above-mentioned copolymers are ratios by weight.

The above copolymers are only examples of the combinations, which can be made with the different monomers, and the invention is not limited at all to the copolymers enu merated.

The different monomers indicated above may be copolymerized according to various methods. For example,

the copolymerization may be conducted in aqueous dispersion containing a catalyst and an activator. Alternatively, polymerization of the monomeric components may occur in bulk without added diluent, or the monomers are allowed to react in appropriate organic solvent reaction media.

The vinylidene chloride copolymers may be coated on the hydrophobic film base according to any suitable technique, e. g., by immersion of the surfaces of the film into a solution of the coating-material. They may also be applied by spray, brush, roller, doctor blade, air brush, orwiping techniques.

. The thickness of the dried layer may vary between-0.3 and 311.

preferably. I

Various wetting or dispersing agents may be used when the vinylidene chloride copolymer layer is applied from an aqueous dispersion. This dispersion is obtained directly when the copolymer has been made by an emulsion polymerization process. When coating aqueous dispersions of vinylidene chloride copolymer on a polyethylene terephthalate film support a very strong adherence to the support is obtained when said dispersions are applied before or during stretching of the polyethylene terephthalate film. The aqueous dispersion may be applied to at least one side of the nonstretched film, but may also be applied to polyethylene terephthalate film, which has been oriented biaxially. The vinylidene chloride copolymer layer may also be coated on at least one side of a polyester film, which was stretched in but one direction, e.g., longitudinally, whereafter the subbed polyester film was stretched in a direction perpendicular thereto in this case transversally.

Finally, the biaxially oriented coated polyester film is provided with the second subbing layer of the mixture of gelatin and butadiene copolymer latex.

The butadiene copolymer comprises 30 to 70 percent by weight of monomeric butadiene units. The balance is formed by units deriving from other ethylenically unsaturated.

hydrophobic monomers e.g., acrylonitrile, styrene, acrylic acid esters, methacrylic acid esters, and acrolein.

The butadiene copolymer is formed by emulsion polymerization and the primary latex obtained is directly mixed with the aqueous gelatin solution in such a way that the ratio of gelatin to butadiene copolymer in the dried layer varies between 1:3 parts and 1:0.5 parts all parts being by weight. To the mixture known plasticizers for gelatin such as polyethylene oxides and glycerol may also be added.

The mixture of aqueous gelatinsolution and of butadiene copolymer latex is coated onto the vinylidene chloride copolymer layer by known means. The thickness of the dried layer generally varies between 0.10 and 2,1,.

The addition of a latex of a. copolymer of butadiene and a lower alkyl ester of acrylic or methacrylic acid to agelatincontaining layer of a photographic material has been described already in the Canadian Pat. specification 748,382 of Gevaert Photo-Producten N.V., issued Dec. 13, 1966. According to this patent specification the butadiene copolymer latex is added to reduce the brittleness of the gelatin layer, to procure a higher dimensional stability to the photographic material, wherein it is used, and to decrease its curling tendency. However, it cannot be deduced from this patent specification that the layer of gelatin and butadiene copolymer latex combined with a vinylidene chloride copolymer layer would procure an adequate subbing combination for any hydrophobic film support, and especially for polyester film supports.

The subbed film support consists of a hydrophobic film support and. the combination of thetwo anchoring subbing layers used according to the invention. As mentioned before the hydrophobic film support may be a film of cellulose triacetate, of polyethylene terephthalate, of polycarbonate, of polystyrene, of polymethacrylic acid ester, etc. The subbed hydrophobic film support may be provided on only one side or on both sides with the combination of subbing layers.

A detailed description will now be given of the composition and structure of a preferred light-sensitive material, and of its use in ,the production according to the present invention of a multicolor image.

A coating composition is prepared containing gelatin dissolved in water wherein (a) selected pigment(s) is or are dispersed in a concentration to yield after. coating and drying a recording layer having an optical density in the wavelength range of maximal absorption of at least 1. The coating composition preferably contains at least 50. percent by weight of gelatin in respect of the pigment particles and a proper amount of plasticizing agent and repellent (a water-attracting compound e.g., glycerol) to provide to the coating a sufficient adherence to its temporary support and to enable its easy wet (aqueous) stripping off from the temporary support, preferably an unsubbed cellulose triacetate support. In addition to said ingredients the coating composition contains an amount of an iron'(lIl) complex compound, which is sensitive toelectromagnetic radiation, preferably iron(IlI) potassium and/or ammonium oxalate having the formulas K Fe(C O,,) and (NH Fe-(C O respectively. The preparation of said compounds is described e.g., in P. Glafkides, Photographic Chemistry, Fountain Press, London, Vol. I (1958) p. 430.

The amount of said iron(lll) complex is such that the gelification of the gelatin is not substantially affected and optimum sensitivity is attained without reaching the concentration, at which the complex salt(s) start(s) to crystallize from the dry layer. A suitable amount of said light-sensitive iron(lll) complex is in the range of 15 to 25 percent by weight in respect of the dry gelatin.

The coating preferably contains 1 tolO g. of gelatin per sq. m. Optimal results are obtained with 3 g. of gelatin per sq. m.

In order to improve the sharpness of the graphic reproduction the gelatin layer may contain a screening dye. The reduction of sensitivity resulting from the presence of said dye may be compensated by the presence of a catalytically polymerizable vinyl monomer or a cross-linking agent for gelatin such as N,N-methylene-bis-acrylamide.

A second coating, the so-called top layer, the composition of which is preferably identical tothe foregoing, except that no pigment(s) are present, is coated on the first one. The second coating preferably contains 1 to 5 g. of gelatin per sq. m. It is, however, not strictly necessary to incorporate a radiation-sensitive ion(lll) complex compound in the said second coating, since a sufficient amount of said compound can diffuse during coating and drying therein from the underlying pigmented layer.

The said second coating forms with the underlying pigmented coating one hardenable double layer firmly bound together, in other words a composite layer which can be transferred as a whole from the temporary support to the permanent support.

A set of materials containing such a composite layer is preferably used for preparing a multicolor color proofing image." A usual set contains yellow, magenta, cyan, and black pigment coatings on separate cellulose triacetate supports.

The permanent support e.g., a polyethylene terephthalate support is successively coated with a first subbing layer on the basisof acopolymer containing hydrophobic structural units in a proper ratio and a second subbing layer, which is more hydrophilic than the first one and contains gelatin, a hydrophobic latex polymer and for giving the support an opaque aspect a white pigment e.g., titanium dioxide particles.

The permanent support preferably applied in color proofing is a hydrophobic polyester resin support subbed with a system of subbing layers as described in the Belgian Pat. specification 72l,469 filed Sept. 27, 1968 by Gevaert-Agfa N.V. The opaque white support has an opacity and whiteness resembling as much as possible the whiteness and opacity of the printing stock whereon the actual print has to be made.

The preparation of a multicolor color proof" then proceeds according to a preferred embodiment as follows.

To the said permanent support subbed as described above the unexposed pigment coating is transferred by pressing the surface of the subbing layer and of the unexposed coating together in the presence of an aqueous liquid and peeling off the temporary cellulose triacetate support.

The pressure step can be carried out in an apparatus, in which the materials involved are pressed together between rollers. A suitable apparatus for that purpose is described in the United Kingdom Pat. application 48,788/68 filed Oct. 15, 1968 by Gevaert-Agfa N.V.

The said apparatus is particularly suitable for use in transferring in wet or moist state colloid layers from a temporary support to a permanent support and such apparatus comprises a pair of cooperating pressure rollers and means for driving said rollers, a first platform for supporting the permanent support prior to its engagement by said pressure rollers, said platform being formed in such a way as to make interrupted or discontinuous contact with the permanent support when this is placed thereon, a second platform arranged over and separated from the first surface for supporting at least the leading part of the temporary support to keep said temporary support separated from a permanent support when this is located on the first platform, the forward ends of both said platforms being disposed proximate to the nip of the pressure rollers so that the supports as they are advanced are gripped by said rollers and progressively pressed together.

After the transfer and drying e.g., with a hot airstream the photohardenable gelatin layer is exposed through a first halftone separation transparency (in the photohardening systems a halftone negative) of the original. In a particular case of four-color printing a cyan pigment coating is first applied to the permanent support and exposed through the cyan printer halftone separation negative of the original. After the exposure the iron(ll) ions formed are oxidized to iron(lII) ions and hardening takes place in the exposed portions, whereupon the nonexposed portions are washed away selectively with a jet of tap water preferably at 30-50 C. In successive order the same steps are carried out for the yellow, magenta, and blackpigmented coating, which are exposed in register on the same support carrying already the cyan pigment coating but respectively through the yellow printer halftone, magenta printer halftone and black printer halftone negative of the original. However, the order wherein the color relief images are made can be chosen arbitrarily.

The exposure, preferably being a vacuum frame contact exposure, is carried out with a light source sufficiently emitting in the ultraviolet range of the spectrum, e.g., with a carbon are, a xenon are, or a high-pressure mercury vapor tube. The duration of the exposure does not only depend on the photosensitivity of the iron(lll) complex but also on the type of the pigment, more particularly on its inherent absorption of ultraviolet radiation and blue light. In order to obtain a halftone relief having an optimal dot sharpness the pigment coating is exposed while being in direct contact with the imagecontaining layer of the transparent original. Less sharp dots are obtained when exposing the pigment coating in direct contact with the support of a silver image transparency used as an original.

The oxidation of the iron(lll) ions is preferably carried out with an aqueous solution of an oxidizing agent or composition producing such agent in situ, e.g., an aqueous solution containing hydrogen peroxide, a water-soluble dichromate e.g., potassium dichromate or a mixture of citric acid and sodium perborate The oxidative treatment is preferably carried out at room temperature and normally lasts no longer than 1 minute. A suitable concentration of hydrogen peroxide is l to 5 percent, of potassium dichromate l to 4 percent and the mixture of sodium perborate and citric acid preferably contains 3 percent by weight of each of these compounds.

it is assumed that during the oxidizing treatment with a percompound, preferably hydrogen peroxide, the following reaction takes place:

The hydroxyl radicals (OI-1) insolubilize the gelatin and other colloids having active hydrogen atoms. The dichromate compound is reduced with iron(ll) ions and yields chromium(Ill) ions acting as insolubilizing agent for gelatin.

The nonhardened gelatin portions are preferably washed off without mechanical rubbing by means of running water at a temperature preferably between 30 and 40 C. The relief image, which has absorbed an amount of water is then dehydrated (unswelled) in a dehydrating liquid e.g., an alcoholic liquid containing to 30 percent by volume of water and 30 to 70 percent by volume of ethanol. Excess of liquid is removed by squeezing the relief between two smooth soft rollers e.g., rubber rollers.

The permanent support carrying the first relief image (the cyan relief image) is pressed between the same rollers while in contact with another pigment coating, e.g., the yellow pigment coating, and after a few seconds of contact the temporary support is peeled off, thus leaving the yellow pigment coating on the cyan part image produced already. The said yellow pigment coating is dried before contact exposure. Drying proceeds e.g., with a warm air current of 40 C.

The whole procedure of exposure (exposure in register), oxidative treatment, washing off, and dehydration is repeated for the yellow coating and the same applies for the magenta image and black printer image.

According to a special embodiment the oxidative treatment and washing off proceeds with or in one liquid.

The obtained colloid pattern or multilayer colloid pattern can be protected and given a glossy appearance by a transparent resin top coat, which according to a preferred embodiment is applied by spraying. A suitable spray cover" consists of polyisobutyl methacrylate.

The invention is illustrated in more details in the following examples, without however limiting it thereto.

EXAMPLE 1 A coating composition was prepared containing the following ingredients:

lg. 10 ml.

The said composition was coated by air knife at a temperature of 37 C. at a rate of 22 sq.m./l. on a cellulose triacetate of 0.1 mm. thickness as the temporary support. The coating formed was gelled by cooling for 1 minute at 8 C.

A top layer without pigment was coated on the gelled coating. Said coating was applied from the following composition:

[0% aqueous solution of gelatin 30 ml. |0% aqueous solution of glycerol 6 ml. 5% aqueous solution of potassium iron (Ill) oxalate 14 ml. Tergitol 4 (trade name) 1.5 ml. water 43 ml.

The said composition was coated by air knife at a temperature of 27 C. at a rate of 30 sq.m./l., gelled, and dried.

The ultraviolet-sensitive pigment material thus obtained had to be transferred to a permanent support consisting of an aluminum sheet whereon on both sides a paper sheet of 90 g./sq.m. was adhered, these paper sheets being covered with a formaldehyde-hardened gelatin coating of g./sq.m.

The operation for obtaining the first pigment image relief then proceeded as follows:

The temporary support of the pigment coating was soaked for 1 minute at room temperature with a mixture of ethanol and water 70:30 percent by volume and thereupon pressed in wet state between soft rollers in contact with the described permanent support. After a contact period of 30 seconds the temporary support was stripped off, thus leaving the cyan pigment coating fixed on the permanent support. The transferred coating was air dried and put in a vacuum frame in contact with the cyan printer separation halftone negative of the original to be printed.

The pigment coating was exposed for 2 minutes with a carbon are light source 1X40 a.) placed at a distance of 70 cm.

The exposed pigment coating was dipped for 30 seconds in a tray containing an aqueous 1 percent hydrogen peroxide solution at 20 C.

The relief was developed by washing without rubbing in running water having a temperature of 35 C. Subsequently, the relief image was dipped for 1 minute in a mixture of ethanol and water (70:30 percent by volume).

A yellow pigment coating being applied to an unsubbed cellulose triacetate temporary support and having the same composition as the cyan pigment coating except for the fact that 4 g. of Pigment Yellow 16 (C.l. 20,040) sold under the name PERMANENT GELB NCG COLANYL TEIG (trade name for a yellow pigment dispersion marketed by Farbwerke l-loechst AG Frankfurt (M), Hochst, W. Germany was substituted for the l g. of HELIOGEN BLAU B COLANYL TElG, was transferred to the cyan relief image by pressing it into contact for 30 seconds with the still wet cyan relief image and stripping off the temporary support.

The whole cycle of exposure and development was repeated, the exposure of the yellow pigment coating being in register with the exposure applied for the cyan coating but lasting, however, 5 minutes.

In the same way also a magenta printer halftone relief image was formed in superposition with the already present cyan and yellow image. The exposure in register of the magenta pigment coating lasted 3 minutes.

The composition of the transferable magenta pigment coating was the same as that of the cyan pigment coating; except for the presence of 1.2 g. of PIGMENT RED 48 (C.l. 15,865) sold under the name LITHOLSCHARLACH BBM PIG- MOSOL (a magenta pigment dispersion marketed by Badische Anilin- & Soda-Fabrik, Ludwigshafen/Rh., W. Germany) instead of 1 g. of HELIOGENBLAU B COLANYL TElG.

A black-printer halftone relief image was formed on the magenta-printer halftone relief image in superposition therewith. The exposure in register of the black pigment coating lasted 8 minutes.

The composition of the transferable black pigment coating was the same as that of the cyan pigment coating except for the presence of 1.5 ml. of a carbon black dispersion prepared by ball milling and dispersing 20 g. of carbon black in 77 ml. of ULTRAVON-W (a heptadecyl-benzimidazole disodium sulphonate dispersing agent marketed by CIBA AG, Basel, Switzerland) and 23 ml. of water, instead of l g. of HELIOGENBLAU G COLANYL TEIG.

As a result of the foregoing procedure a four color color proof image of the color image to be printed was obtained. Said image was of high quality with respect to the dot sharpness.

EXAMPLE 2 Example 1 was repeated, with the proviso however, that use was made of a permanent support consisting of a paper sheet made water impermeable by a treatment with a cellulose nitrate lacquer coated successively with a subbing layer for gelatin and with a formaldehyde-hardened gelatin coating of 3 g. per sq. m. I

EXAMPLE 3 Example 1 was repeated but instead of potassium iron(lll) oxalate a same amount of ammonium iron(lll) oxalate was used. The exposure times were doubled. A residual staining due to iron(lll) ions left in the developed relief was bleached out by dipping the finished multirelief print for 1 minute at 20 C. in a 5 percent aqueous solution of sodium hexametaphosphate and rinsing in running water for 2 minutes.

EXAMPLE 4 Example 1 was repeated but instead of 23 ml. of a 5 percent aqueous solution of potassium iron(lll) oxalate 20 ml. of ammonium iron(lll) oxalate were used. A screening dye viz 1 ml. of a 5 percent aqueous solution of tartrazine (C.l. 19,140) was incorporated into the cyan and magenta pigment coating. In order to compensate for the decrease in sensitivity caused by the presence of the screening dye a mixture of acrylamide and N,N-bis-methylene acrylamide in a ratio by weight of 7 to 3 was added to the pigment coating in an amount of 10 percent by weight calculated on the gelatin.

EXAMPLE 5PART C A blue layer sensitive to ultraviolet radiation was prepared by allowing to swell 63 g. of gelatin in 494 ml. of water and melting the gelatin at 5055 C., whereupon the following composition was added while stirring:

l5.5 ml.

I26 ml.

l2.5 ml.

The resulting composition was coated by air knife at a temperature of 35 C. at a rate of 23 sq.m./l. to a temporary support of unsubbed cellulose triacetate having a thickness of 0.1 mm. The solution was gelled at 8 C. To the gelled layer a protective layer was coated by air knife. The coating composition of the protective layer was formed by allowing to swell 27 g. of gelatin in 768 ml. of water, adding a 10 percent by weight dispersion of colloidal silica (average particle size: 23u) in an 8 percent by weight aqueous solution of gelatin, melting at 45-48 C. and adding successively:

l0% by weight aqueous solution of glycerol 60 ml. 5% by weight aqueous solution of saponine 20 ml.- 1 Tergitol 4 (trade name) l5 ml. i

7.5% by weight aqueous solution of ammonium iron (lll) oxalate ml.

The coating composition was applied at 24 C. at a ratio of 30 sq.m./l. and after coating the protective layer was gelled and dried.

The resulting light-sensitive layer was transferred as described further on to an opaque permanent support of polyethylene terephthalate, which was subbed at both sides as follows:

Both sides of a biaxially stretched polyethylene terephthalate film having a thickness of 180;}. were coated with the following composition at 2530 C. at a ratio of 1.6 g./sq.m.:

copolymer of vinylidcne chloride, N-tert.-butylacrylamide, n-butyl acrylate, and N-vinylpyrrolidone (ratios by weight: 70:23:3z4) 5.5 g. methylene chloride 65 ml. 1,2-dichloroethane 35 ml.

The resulting layer was coated with a mixture prepared as follows:

1,350 g. of titanium dioxide (average particle size: 0.11 1.) were dispersed in l. of water containing 25 ml. of DEQUEST 2006 (trade name of Monsanto Chemical Company, St. Louis, Mo., U.S.A. for a dispersing agent corresponding to the following structural formula:

The dispersion was stirred rapidly for minutes at a temperature of 5l 5 C. and then heated to 35 C., at which temperature 400 ml. of a 10 percent by weight aqueous solution of gelatin was added, while continuing the rapid stirring. Subsequently the following composition was added by stirring slowly to avoid scumming:

a 10% by weight aqueous solution of gelatin L300 ml. water 130 ml. by weight latex (aqueous dispersion) of the copolymer of butudiene and methyl methacrylate (ratio by weight 50:50) 2,500 ml. 10% by weight aqueous solution ofthe sodium salt of oleyl methyltauride 37.5 ml. ethylene ehlorohydrin 500 ml.

The coating was carried out at such a rate that upon drying a layer of 5 was obtained.

The white permanent support was immersed for at least 90 seconds in an aqueous solution of an alcohol, e.g., ethanol (an aqueous solution of isopropanol or n-propanol can be used also). The proportion by volume between the alcohol and water may vary between 1/1 and 6/1. The proportion of 2/1 is preferred.

The wetted permanent support was pressed in contact with the light-sensitive layer (the pressure can be effected by means of a hand roller or two rollers driven by a motor). After the transfer the temporary support was stripped off.

The layer was dried in a hot airstream not exceeding 60 C.

The light-sensitive layer was contact exposed through the cyan printer halftone separation negative of the multicolor image to be reproduced to an ultraviolet radiation-emitting arc lamp.

The exposure was carried out with an arc lamp of 1X40 a. placed at a distance of 70 cm.; the exposure time was 3 minutes. If the material was held in adequate contact by the exposure frame it was not liable to overexposure. Such overexposure may attain 10 times the value of a sufficient exposure time, without a worsening of the quality and the reproducibility of the final product.

After exposure the light-sensitive layer was dipped for at least seconds in an oxidizing solution at 2025 C. The oxidizing solution was a peroxide bath containing 0.5 to 5 percent of hydrogen peroxide.

The colloid relief pattern was developed by washing away the nonhardened gelatin without rubbing in running water of 30-50 C., preferably having a temperature of 35-40 C.

After washing away of the nonhardened gelatin, the cyan relief pattern obtained was immersed before the application thereto of a next colloid layer in an alcohol-water bath having the same composition as that used for wetting the permanent support.

EXAMPLE 5Part C The cyan relief pattern obtained was coated with a ultraviolet-sensitive yellow layer having the following composition:

gelatin 63 g.

water 374 ml.

a 5% aqueous solution of Ultravon W (trade name) 15.5 ml. B.

Hansayellow G 30 Colanyl (Cl.

a 10% by weight aqueous solution ofglycerol 94.5 ml.

B was added to A while stirring. To the resulting mixture the following compounds were added:

water 595 ml. 10% by weight aqueous solution ofsaponine 10 ml. 5% by weight aqueous solution of the sodium salt oforthosulfobenzoic acid dodecafluoroheptyl ester 6 ml. aqueous 7.5% by weight solution of ammonium iron (lll) oxalate 336 ml.

The solution was coated by air knife on an unsubbed cellulose triacetate support having a thickness of 0.1 mm. at a temperature of 35 C. at a ratio of 23 sq.m.Il. The solution was gelled at 8 C. To the gelled layer a protective layer was coated by air knife from a composition prepared as follows:

gelatin 27 g. water 748 ml. a 10% by weight dispersion of colloidal silica (average particle size 2-3 in an 8% by weight aqueous solution of gelatin 30 g.

The mixture was allowed to melt whereupon the following compounds were added:

5% aqueous solution of saponine 20 ml. Tergitol 4 (trade name) 15 ml. aqueous 7.5% by weight solution of ammonium iron (lll) oxalate ml.

The application on the temporary support was performed as described in part C,. The light-sensitive yellow layer was transferred to the permanent support onto the already existing cyan printer image. The transfer was carried out according to the same technique as described above for the cyan layer. The light-sensitive yellow layer was exposed to the halftone separation negative of the yellow printer image and further processed in the same way as the cyan layer.

EXAMPLE 5-Part C 1 A light-sensitive magenta layer was transferred to thle yellow relief pattern of the wetted permanent support. This layer had the following composition:

same composition as that given in part C, B.

Litholscharlach BBM Pigmosol (trade name) 9 g.

% aqueous solution of Ultravon W (trade name) 16 ml. by weight aqueous solution ofglycerol 126 ml.

To the mixture of A and B were added 69.5 ml. of water. Subsequently the ingredients stated under C were added thereto.

The light-sensitive layer was then finished and processed as described in part C EXAMPLE 5Part C The light-sensitive black layer was now transferred to the permanent support carrying three color images already. The

The following compounds were then added to the mixture of A and B:

water 71.2 ml. aqueous 10% by weight solution of saponine l2.5 ml. 5% by weight aqueous solution of the sodium salt of orthosulfobenzoic acid dodecafluoroheptyl ester 6 ml. 7.5% by weight aqueous solution of ammonium iron (ill) oxalate 252 ml.

This solution was coated by air knife on an unsubbed cellulose triacetate temporary support at a temperature of 35 C. at a ratio of 23 sq.m./l. The solution was gelled at 8 C. To the gelled layer a protective layer was coated by air knife from a composition prepared as follows:

gelatin 27 g. water 788 ml. :1 10% by weight dispersion of colloidal silica (average particle size 2-3 .4) in an 8% by weight aqueous solution of gelatin 30 g. The following compounds were added to A: l()% by weight aqueous solution of saponine 20 ml. Tergitol 4 (trade name) l5 ml. 7.5% by weight aqueous solution of ammonium iron (lll) oxalate 120 ml.

The protective layer was coated at 24 C. at a ratio of 30 sq.m./l. After gelling the layer was dried.

The resulting light-sensitive layer was transferred and finished as described in part C The developed image was dipped in an alcohol/water bath (volume ratio: 70/30), adhering moisture was raked off and finally the image was dried.

The result was a four color proofing image having the same colors as if it were printed. The multicolor image offered a true reproduction of the separation negatives, and contained very sharply reproduced dots, the size of which was a true reproduction of the dots present in the separation negatives serving as originals in the exposure.

EXAMPLE 6 The colloid recording layers of the Example 5-part C were processed as described in said example except for the treatment in the oxidizing solution which according to the present example was a 2 percent by weight aqueous solution of potassium bichromate.

The exposed layers were dipped for 30 seconds at 20 C. in said solution. A longer contacting time with the solution had no influence on the quality of the obtained images. Same results were obtained with aqueous solutions containing from 1 to 8 percent by weight of ammonium bichromate.

EXAMPLE 7 Example 5 was repeated except for the fact that in the composition of the colloid recording layers the aqueous 7.5 percent by weight solution of ammonium iron(lll) oxalate was replaced by a same volume of an aqueous 4 percent by weight 4,4'-diazido-stilbene-2,2-disulphonic acid sodium salt solution. The transfer of the differently colored colloid layers proceeded as described in Example 5. The exposure times have, however, to be doubled.

The processing of the exposed colloid layers producing a relief image corresponding with the exposed parts was a simple washoff treatment under running warm water (40 C.

After each washoff step, the obtained relief pattern was immersed for partly dehydrating in an ethanol water mixture (2/1 by volume).

The result was a four color proofing image having the same colors as if it were printed.

We claim:

1. A process for producing on a permanent support a colored image by means of at least one colored hydrophilic colloid layer that can be hardened by chromium(lll) ions or by a reaction product resulting from the reaction of iron(ll) ions and hydrogen peroxide, said process comprising for each such layer the steps in sequence of:

1. transferring an unhardened colored hydrophilic colloid layer which contains a photosensitive iron(lII) complex compound that on exposure to active electromagnetic radiation yields iron(ll) ions, from a relatively hydrophobic temporary support to said permanent support by pressing it in the presence of an aqueous liquid against said colloid layer, and removing the temporary support, thus leaving said layer on the permanent support,

2. exposing the transferred colloid layer in substantially dry state to imagewise modulated active electromagnetic radiation,

3. treating the exposed layer with an aqueous hardening liquid comprising hydrogen peroxide, or with an aqueous liquid containing dichromate ions to effect hardening of the exposed regions of said colloid layer,

4. removing the nonexposed regions of the colloid layer from said permanent support by washing with an aqueous liquid.

2. A process according to claim 1 wherein a multicolor pattern is produced by repeating the steps (1), (2), (3) and (4) with a plurality of hydrophilic colloid layers having different colors and wherein the treatment of each exposed colloid layer containing iron(ll) ions in the exposed portions with said aqueous hardening liquid results in anchoring of the exposed portions of each colloid layer to the corresponding colloid portions of the previously formed underlying hydrophilic colloid pattern.

3. A process according to claim 1 wherein the photosensitive compound is an iron(lll) complex compound, which on exposure to said radiation yields iron(ll) ions and which is of the type wherein the iron(IlI) ions are complexed with a moiety having an electromdonating character relative to an ironflll) ion.

4. A process according to claim 1 wherein the photosensitive compound is an iron(lll) complex derived from a polybasic acid and has the formula (FeA,,) in which n is the number of acid molecules, z is the valency of the organic acid, and x that of the resulting complex ion.

5. A process according to claim 4 wherein the photosensitive iron(IlI) complex compound is an iron(lll) complex oxalate, tartrate, or citrate.

6. A process according to claim 1 wherein the colloid layer contains a water-soluble hydrophilic colloid polymer having active hydrogen atoms.

7. A process according to claim 1 wherein the colloid layer contains a water-soluble hydrophilic colloid polymer capable of undergoing sol-gel transformation.

8. A process according to claim 1 wherein said colloid layer comprises gelatin.

9. A process according to claim 1 wherein said colloid layer contains a hydrophilic plasticizing agent.

10. A process according to claim 1 wherein the hardenable colloid layer contains a substance that imparts to the colloid layer the property of a weaker adherence to the temporary support in wet state than in dry state.

11. A process according to claim 1 wherein the hardenable colloid layer contains a polyol.

12. A process according to claim 1 wherein the hardenable colloid layer contains glycerol.

13. A process according to claim 1 wherein the temporary support is a flexible support.

14. A process according to claim 1 wherein the temporary support is an unsubbed cellulose triacetate film sheet.

15. A process according to claim 1 wherein the permanent support is flexible.

16. A process according to claim 1 wherein the permanent support is a hydrophobic resin support carrying an external subbing layer having hydrophilic properties.

17. A process according to claim 16 wherein said permanent support is a hydrophobic film support having superposed thereon in succession a layer (A) directly adherent to said hydrophilic film support and comprising a copolymer formed from 45 to 99.5 percent by weight of at least one ofthe chlorine-containing monomers vinylidene chloride and vinyl chloride, from 0.5 to percent by weight of an ethylenically unsaturated hydrophilic monomer, and from O to 54.5 percent by weight of at least one other copolymerizable ethylenically unsaturated monomer, and a layer (B) comprising in a ratio of 1:5 to 1:05 by weight a mixture of gelatin and a copolymer of to 70 percent by weight of butadiene with at least one copolymerizable ethylenically unsaturated monomer.

18. A process according to claim 16 wherein said permanent support carries a coating comprising white pigment particles in a binder.

19. A process according to claim 16 wherein the permanent support is a polyethylene terephthalate support.

20. A process according to claim 1 wherein the colloid relief pattern is treated with a mixture of a water-attracting alkanol and water to reduce its swelling.

21. A process according to claim 1 wherein each such colored hardenable colloid layer on its temporary support is covered with an uncolored top layer containing the same colloid as the colored colloid layer.

22. A process according to claim 21 wherein the top layer has the same composition as the colored hardenable colloid layer except for the colored substances contained therein.

23. A process according. to claim 1 wherein each such colored hardenable colloid layer has a thickness in the range Of115[1..

24. A process according to claim 1 wherein each such colored hardenable colloid layer contains dyes that are resistant to diffusion.

25. A process according to claim 24 wherein said dyes are pigments that are dispersible in water.

26. A process according to claim 1 wherein the hardenable colloid layer contains acrylamide as polymerizable monomeric compound and/or N,N'-methylene-bis=acrylamide as crosslinking agent.

27. A process for the production ofa multicolor halftone color proofing print by means of hydrophilic colored colloid layers which can be hardened by a reaction product resulting from the reaction of iron(ll) ions and hydrogen peroxide,

which process includes the steps of:

l. transferring an unhardened cyan colored hydrophilic colloid layer, which contains gelatin and a photosensitive iron(III) complex compound that on exposure to active electromagnetic radiation yields iron(Il) ions, from a temporary support to a permanent support by pressing it in the presence of an aqueous liquid against the same layer and removing the temporary support, thus leaving the said layer on the permanent support,

2. exposing the transferred colloid layer to active electromagnetic radiation through a cyan printer black-andwhite separation halftone negative transparency of a multicolor original to be reproduced by printing,

. treating the exposed layer with an aqueous liquid comprising hydrogen peroxide,

4. removing the unexposed portions of the transferred colloid layer by washing with a aqueous liquid to give a cyan colored relief pattern on said support,

5. repeating the steps of transferring, exposing, hydrogen peroxide treatment and washing with a yellow, magenta, and black colored colloid layer in any order so that on the same permanent support a halftone multicolor image of superposed colored colloid relief patterns is produced, the different exposures being carried out in register through the yellow printer, magenta printer, and black printer black-and-white halftone separation negatives. 

2. A process according to claim 1 wherein a multicolor pattern is produced by repeating the steps (1), (2), (3) and (4) with a plurality of hydrophilic colloid layers having different colors and wherein the treatment of each exposed colloid layer containing iron(II) ions in the exposed portions with said aqueous hardening liquid results in anchoring of the exposed portions of each colloid layer to the corresponding colloid portions of the previously formed underlying hydrophilic colloid pattern.
 2. exposing the transferred colloid layer to active electromagnetic radiation through a cyan printer black-and-white separation halftone negative transparency of a multicolor original to be reproduced by printing,
 2. exposing the transferred colloid layer in substantially dry state to imagewise modulated active electromagnetic radiation,
 3. treating the exposed layer with an aqueous hardening liquid comprisinG hydrogen peroxide, or with an aqueous liquid containing dichromate ions to effect hardening of the exposed regions of said colloid layer,
 3. treating the exposed layer with an aqueous liquid comprising hydrogen peroxide,
 3. A process according to claim 1 wherein the photosensitive compound is an iron(III) complex compound, which on exposure to said radiation yields iron(II) ions and which is of the type wherein the iron(III) ions are complexed with a moiety having an electron-donating character relative to an iron(III) ion.
 4. A process according to claim 1 wherein the photosensitive compound is an iron(III) complex derived from a polybasic acid and has the formula (FeIIIAnz)x in which n is the number of acid molecules, z is the valency of the organic acid, and x that of the resulting complex ion.
 4. removing the unexposed portions of the transferred colloid layer by washing with a aqueous liquid to give a cyan colored relief pattern on said support,
 4. removing the nonexposed regions of the colloid layer from said permanent support by washing with an aqueous liquid.
 5. repeating the steps of transferring, exposing, hydrogen peroxide treatment and washing with a yellow, magenta, and black colored colloid layer in any order so that on the same permanent support a halftone multicolor image of superposed colored colloid relief patterns is produced, the different exposures being carried out in register through the yellow printer, magenta printer, and black printer black-and-white halftone separation negatives.
 5. A process according to claim 4 wherein the photosensitive iron(III) complex compound is an iron(III) complex oxalate, tartrate, or citrate.
 6. A process according to claim 1 wherein the colloid layer contains a water-soluble hydrophilic colloid polymer having active hydrogen atoms.
 7. A process according to claim 1 wherein the colloid layer contains a water-soluble hydrophilic colloid polymer capable of undergoing sol-gel transformation.
 8. A process according to claim 1 wherein said colloid layer comprises gelatin.
 9. A process according to claim 1 wherein said colloid layer contains a hydrophilic plasticizing agent.
 10. A process according to claim 1 wherein the hardenable colloid layer contains a substance that imparts to the colloid layer the property of a weaker adherence to the temporary support in wet state than in dry state.
 11. A process according to claim 1 wherein the hardenable colloid layer contains a polyol.
 12. A process according to claim 1 wherein the hardenable colloid layer contains glycerol.
 13. A process according to claim 1 wherein the temporary support is a flexible support.
 14. A process according to claim 1 wherein the temporary support is an unsubbed cellulose triacetate film sheet.
 15. A process according to claim 1 wherein the permanent support is flexible.
 16. A process according to claim 1 wherein the permanent support is a hydrophobic resin support carrying an external subbing layer having hydrophilic properties.
 17. A process according to claim 16 wherein said permanent support is a hydrophobic film support having superposed thereon in succession a layer (A) directly adherent to said hydrophilic film support and comprising a copolymer formed from 45 to 99.5 percent by weight of at least one of the chlorine-containing monomers vinylidene chloride and vinyl chloride, from 0.5 to 10 percent by weight of an ethylenically unsaturated hydrophilic monomer, and from 0 to 54.5 percent by weight of at least one other copolymerizable ethylenically unsaturated monomer, and a layer (B) comprising in a ratio of 1:5 to 1:0.5 by weight a mixture of gelatin and a copolymer of 30 to 70 percent by weight of butadiene with at least one copolymerizable ethylenically unsaturated monomer.
 18. A process according to claim 16 wherein said permanent support carries a coating comprising white pigment particles in a binder.
 19. A process according to claim 16 wherein the permanent support is a polyethylene terephthalate support.
 20. A process according to claim 1 wherein the colloid relief pattern is treated with a mixture of a water-attracting alkanol and water to reduce its swelling.
 21. A process according to claim 1 wherein each such colored hardenable colloid layer on its temporary support is covered with an uncolored top layer containing the same colloid as the colored colloid layer.
 22. A process according to claim 21 wherein the top layer has the same composition as the colored hardenable colloid layer except for the colored substances contained therein.
 23. A process according to claim 1 wherein each such colored hardenable colloid layer has a thickness in the range of 1-15 Mu .
 24. A process according to claim 1 wherein each such colored hardenable colloid layer contains dyes that are resistant to diffusion.
 25. A process according to claim 24 wherein said dyes are pigments that are dispersible in water.
 26. A process according to claim 1 wherein the hardenable colloid layer contains acrylamide as polymerizable monomeric compound and/or N,N''-methylene-bis-acrylamide as cross-linking agent.
 27. A process for the production of a multicolor halftone ''''color proofing'''' print by means of hydrophilic colored colloid layers which can be hardened by a reaction product resulting from the reaction of iron(II) ions and hydrogen peroxide, which process includes the steps of: 